This invention relates to the formation, separation, and modification of solids derived from raw cheese whey, and particularly from raw acid cheese whey.
In addition, this invention relates to the modified dried whey obtained by the process of this invention and its use in food products and particularly bakery products.
Cheese whey is generally defined as the liquid byproduct from the manufacturer of cheese and casein. Basically, cheese whey is the byproduct obtained by the acid, or rennet coagulation of milk protein (i.e., casein) from milk. The whey obtained from the acid coagulation is called acid whey and that obtained from rennet, sweet whey.
The acid coagulation of milk protein from milk involves either the addition of lactic acid producing bacteria (e.g., Lactobacillus sp.) or the addition of mineral acid (i.e., direct acidification). Regardless of the method used to acidify milk, acidification is allowed to proceed until a pH of about 4.6 is reached. At this pH, casein becomes insolubilized and coagulates as cheese. The cheese produced by using lactic acid is commonly known as cottage cheese. The whey obtained by the separation and removal of this cheese curd is called cottage cheese whey. The whey obtained by direct acidification of milk with mineral acid is commonly known as casein whey.
Sweet cheese whey is obtained by the separation and removal of coagulated casein produced by the addition of a proteolytic enzyme to milk. The proteolytic enzymes generally used are known as rennin and/or pepsin. The addition of one or both of these enzymes to milk soon thereafter causes the coagulation of casein. The cheese curd thus produced is the product of the enzymatic coagulation of casein. Specific examples of cheese products produced by this general method are cheddar cheese, swiss cheese and mozzarella cheese.
It is known that acid cheese whey contains whey proteins, milk sugar (lactose), and salts in substantially the same form as that contained in the original milk. In contrast, sweet cheese whey, since it is obtained from the enzymatic coagulation of milk protein, contains whey proteins, milk sugar (lactose), salts, and an unknown component. The unknown component is presumably related to the proteolytic enzyme used in this method of cheese production. Processing of acid and sweet cheese whey, therefore, must take into consideration the chemical differences in these two types of cheese whey.
Various membrane processing techniques are currently used to separate cheese-whey solids, for example, gel filtration, ultra filtration, reverse osmosis, and electrodialysis may be used. Since the above mentioned processes separate whey solids on a molecular weight basis by using semi-permeable membranes, any molecular constituent in the raw whey which tends to clog the semi-permeable membrane, creates inefficiency of operation. It is, therefore, desirable to remove by pretreatment the constituent responsible for clogging the semi-permeable membrane.
Several pretreatment methods are currently used in an attempt to resolve this problem. One of these can be described as additional centrifugal clarification of raw cheese whey. This method removes insoluble material originally contained in raw cheese whey. However, this method does not remove solubilized constituents that tend to clog the membrane.
Another known method used to remove soluble constituents from cheese whey by pretreatment purposes is disclosed in U.S. Pat. No. 3,560,219. This process discloses the addition of divalent metal ion to calcium deficient raw cheese whey, the neutralization of pH by the addition of caustic, and the removal of the precipitate thus formed. Although, the process disclosed in this patent removes solubilized lipid from raw whey, the addition of divalent ion to raw whey requires an additional step in the separation and recovery of whey solids. Furthermore, divalent metal ion addition to raw whey may upset the ionic equilibrium among the major constituents obtained by membrane processing. The finally separated whey protein may exhibit off flavor due to the divalent metal ion addition to the raw whey. However, this problem is solved by the present invention.
With reference to the use of whey products in human food systems, it has been desirable to attempt to replace nonfat dry milk solids in various bakery products. However, it is known that whey solids generally do not function as nonfat milk solid substitutes in human food systems.